1. Field of the Invention
The present invention relates to a method and to an apparatus for the substantially uniform irradiation of the entire area of cavities from the inside. The method and apparatus are used to irradiate the walls of cavities such as, for example, internal hollow organs, with light. Uniform light distribution over the entire wall of the cavity is important in this connection.
2. Technology Review
Homogeneity is required, for example, for the integral photodynamic treatment of photo-sensitized tumors with laser light. A light dose that is too low locally does not completely kill off the tumor at that location and results in recurrences. Too high a light dose also damages healthy wall regions. Under certain circumstances, the tolerance range for the light dose is rather narrow.
Published application Ser. No. DE-OS 3,323,365 A1, which appears to correspond to U.S. Pat. No. 4,612,938, proposes a device in which a centrally ending glass fiber is inserted to transport light into spherical hollow organs, e.g. a urinary bladder. A liquid scattering medium filling the organ provides the homogeneity. A similar device is disclosed in Jocham et al, "Porphyrin Localization and Treatment of Tumors," 249-256 (1984).
Star et al, Photochemistry and Photobiology 46, No. 5, 619-624, (1987), irradiate cavities by means of a centrally placed radiator having an approximately cupola-shaped radiation characteristic.
Arnfield et al, "Lasers in Surgery and Medicine" 6, 150-156, (1986), describe a radiator having a cylindrical radiation characteristic that is inserted axially into cylindrical organs.
All of these devices require great accuracy in centering the central or axial radiator. Due to breathing and heartbeat movements, this accurate positioning is often almost impossible to accomplish, particularly in situations in which the irradiation device must be introduced into the cavity through a narrow catheter. Moreover, high demands are placed on the homogeneity of the radiation characteristic of these radiators which in most cases is imperfectly met.
Another drawback of these devices is that if the shape of the cavities deviates from the sphere or cylinder, these devices provide unsatisfactory results even if optimally adjusted.
It is an object of the invention to develop a method and an apparatus for the homogeneous irradiation of cavities in which irradiation homogeneity for different cavity shapes is ensured substantially independently of the position of the radiation source within the cavity.